Diffuser system for abrasive blaster

ABSTRACT

A shutdown system for a media blast system includes a normally closed diverter path which remains closed to air flow during operation of the blast system. During shutdown, the air flow to the metering valve is shut off, shutting off the system. At the same time, the diverter path is opened, relieving pressure in the supply line by permitting pressurized air and abrasive in the supply line to back flow through the diverter from which it is exhausted, almost instantaneously shutting off flow through the nozzle. A diffuser system is included for receiving and exhausting residual abrasive media and for reducing the noise level of the exhausted air.

BACKGROUND OF THE INVENTION Field of the Invention

The subject invention is related to abrasive blasting systems wherein an abrasive media is released under pressure through a nozzle, and is controlled by a metering valve, generally referred to as abrasive blasters. The invention is specifically directed to a shut-off system for closing the valves to stop the flow of air through the metering valve and the nozzle.

Discussion of the Prior Art

Abrasive blasters are well-known. Typically a system includes a vessel or pressure tank for housing a source of abrasive media and a source of pressurized air. When the air is released through a metering valve, it draws the abrasive media into the stream and releases it to an outlet nozzle. The amount of abrasive media released is controlled by the metering valve. Examples of metering valves are valves such as the Thompson Valve II, MV 2, MicroValve, and Thompson Valve manufactured by Axxiom Manufacturing, Inc. of Fresno, Tex.

Typically, blast outlets at the nozzle are shut off by closing valves to stop the flow of air and abrasive. Generally, a deadman control switch is coupled to the system to control the opening and closing of the valves and the flow of air and abrasive through the blast nozzle. However, once the deadman control is released to the shutdown position, the energy in the supply or blast hose must still dissipate through the blast nozzle.

In practice a one and one-half inch blast hose with a half inch nozzle at two hundred feet will take as long as 10-15 seconds for the supply pressure to dissipate down to a non-aggressive level. During this time the system is shutdown but an aggressive residual flow continues through the outlet nozzle.

It is desirable to reduce the residual flow once the system is shutdown.

SUMMARY OF THE INVENTION

The subject invention is directed to a shutdown system that depressurizes the blast pressure in a supply hose to a non-aggressive level in as short a time as one second or less in a two hundred foot supply hose running from the metering valve to the nozzle. A diffuser is utilized in combination with the shutdown system to reduce the noise level and dissipate energy associated with the air and abrasive exhausted from the system during shutdown mode. In a typical example the inlet pressure line is one and one half inches in diameter and outlet supply hose is also one and one half inches in diameter. These are connected to the blast nozzle which is one half inch in diameter. Shutdown without the shutdown system can last as long as 10-15 seconds, with the air and abrasive released at the nozzle at aggressive levels through much of this time. The shutdown diverter reduces this time to one second or less. This is better than a 10:1 improvement in shutdown time. The quick release of air and abrasive during shutdown produces an unacceptable noise level. The subject invention includes a diffuser for expanding, redirecting and releasing the air and abrasive through a baffle for mitigating the noise level.

Specifically, the subject invention is directed to a diverter/diffuser system for a media blasting system of the type having an air operated media metering valve for releasing a mixture of pressurized air and media through a downstream nozzle. The diverter/diffuser system of the preferred embodiment includes a diverter pressure line connected to the metering valve and the diverter/diffuser system. The diverter includes a diverter switch such as a pinch ram for opening and closing air and abrasive flow to the diverter/diffuser system. The pinch ram is normally in the closed position during operation, and the pressurized air flow is directed through the nozzle. The pinch ram is opened during shutdown mode the air and abrasive is diverted to a diffuser for exhausting it from the system and for releasing the pressure in the metering valve and the nozzle.

The diffuser of the subject invention includes a flow restrictor pathway for expanding and for reducing the noise level of the exhausted air. In the preferred embodiment the flow restrictor is a baffle plate in the path of the air and abrasive flowing through the diverter. The diffuser includes a deflector element wear plate which absorbs energy from the residual flow, including any residual media, and redirects the residual flow to a baffle or silencer for reducing the noise generated by the exhausted air. Preferably, the deflector element is removable and replaceable. In the preferred embodiment the deflector element is upstream of the flow restrictor.

The diverter path is normally closed and remains closed during operation of the blast system. In typical manner the pressurized air flow is input to the metering valve and draws abrasive media from the media storage vessel for releasing the air pressurized media flow through the blast nozzle. During shutdown, the pressurized air and abrasive flow to the metering valve is shut off, shutting off the system. At the same time, the diverter path is opened, relieving pressure in the delivery line by permitting pressurized air and abrasive in the line, metering valve and nozzle to back flow through the diverter from which it is exhausted, almost instantaneously shutting off flow through the nozzle.

In the subject invention, the reverse flow is directed into a blowdown diffuser. This is an expansion system and a silencer system for reducing the noise level of the exhaust. In the preferred embodiment, the diffuser also includes a deflection plate or element for deflecting any residual media in the exhausted air flow. The deflection plate is preferably made of a replaceable material such as polyurethane and can be readily replaced upon wear.

The system can be used with a single metering valve configuration or may be scaled up to support a multi-valve system. Specifically, the diffuser is scaled up to include multiple inlet ports for receiving reverse flow, diverted pressurized air and abrasive when any or all of the blast nozzles are shutdown.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of a typical blaster system with a diverter and with the diffuser of the subject invention, here shown as installed on in a single metering valve system.

FIG. 2 is a side view, partially cutaway, showing the air and abrasive flow when the metering valve and nozzle are in operation.

FIG. 3 is a section view taken along line A-A of FIG. 2 and shows the position of the diverter pinch ram during metering valve and nozzle operation.

FIG. 4 is a view similar to FIG. 2, showing the air and abrasive flow when the nozzle is in shutdown mode and the diverter pinch ram is opened to permit air and abrasive flow to the diffuser.

FIG. 5 is a section view similar to FIG. 3, taken along line B-B of FIG. 4 and shows the diffuser during shutdown procedure.

DETAILED DESCRIPTION

An exemplary configuration of the diverter/diffuser system 10 of the subject invention is shown in FIGS. 1 and 2. A supply of pressurized air or other pressure media is provided via a supply line 19 and is introduced into the diverter valve 20 and into the metering valve 28 via line 23. Control lines 11 and 13 control the diverter valve 20 and the metering valve 28, respectively. In the exemplary embodiment, the metering valve is a Thompson II valve and the diverter valve is a ComboValve, both manufactured under the Schmidt brand name by Axxiom Manufacturing, Inc. of Fresno, Tex. It will be readily understood by those skilled in the art that other valves with similar functional features could be readily substituted.

The abrasive media is stored in the pressure vessel 40, which is pressurized via pressure line 41.

The inlet air in line 19 is introduced into a normally open diverter control valve 20. In the exemplary embodiment, the diverter control valve 20 includes a pinch ram 22 which is in contact with the flexible pressure line 24. The valve operating gate or pinch ram 22 is shown closed in FIG. 2, which is during the operation mode. During blasting operation, the pressurized air in line 19 flows through the valve 20 and through line 23 and the Y-connector 31 to provide supply air to the metering valve 28. The metering valve 28 then releases an air/media mix through valve outlet 30 and through nozzle 33.

During shutdown (see FIG. 4), the pressurized flow in control line 11 is reduced to permit the pinch ram 22 to open and the flow in control line 13 closes metering valve 28. Once the pinch ram is lifted and opened, the restriction on line 24 is removed, the residual pressurized air and abrasive in line 37, metering valve 28 and any upstream air and is diverted back through the Y-connector 31 toward the diverter 20 and into the diffuser 36.

By releasing pinch ram 22 on diverter valve 20 (see FIG. 4) the residual pressurized in line 24 and in the downstream metering valve 28 can back flow through line 24 and into the diffuser 36. This almost instantaneously reduces the pressure at metering valve outlet port 30, and hence the nozzle 31, to a non-aggressive level, reducing or almost eliminating the lag time between initiation of shutdown and completion of shutdown.

As shown in FIGS. 2 and 3 during blasting operation and in FIGS. 5 and 6 during shutdown mode, the diffuser is a closed chamber or box having an inlet port 50. The box in the exemplary embodiment includes an upper expansion chamber 60 and a lower chamber 62. A flow restrictor plate 63 is provided between the chambers to slow the flow of air and abrasive and redirect it into the expansion chamber. The lower chamber 62 includes a deflector/wear element or plate 52, mounted between the chamber 62 and a removable cap 59. A baffle plate 58 (as best shown in FIGS. 3 and 5) is provided for reducing the noise level of the exhausted air and abrasive before it is exhausted at exhaust port 64. The baffle plate is shown in a cut-away view. It should be understood that the plate covers the entire cross-sectional area of the upper chamber 60. Where desired, the upper chamber 60 may include a sound-deadening liner 61 to further reduce the noise. A sound deadening line may also be incorporated in the lower chamber 62.

During shutdown the diverted air and abrasive flows past open pinch ram 22 of diverter valve 20 and into the diffuser 36 through port 50. It first impinges on the deflector element 52 for slowing the air flow and any residual abrasive media and then flows upwardly around the restrictor plate 63 and into the upper expansion chamber 60. It flows through the silencer baffle plate 58 and is exhausted through exhaust port 64.

While certain features and embodiments of the invention have been described in detail herein, it should be understood that the invention includes all modifications and enhancements within the scope and spirit of the following claims. 

What is claimed is:
 1. A diverter/diffuser system for a media blasting system of the type having an air operated media metering valve for releasing a mixture of pressurized air and media through a downstream nozzle, the diverter/diffuser system comprising: a. A diverter pressure line connected to the metering valve and the diverter/diffuser system; b. A diverter switch for opening and closing air and abrasive flow to the diverter/diffuser system, wherein the switch is normally in the closed position during operation and is opened during shutdown mode; c. A diffuser for receiving the air and abrasive flowing through the diverter system and expanding and exhausting it from the system.
 2. The diverter/diffuser system of claim 1, wherein the diffuser includes a flow restrictor for reducing the noise level of the exhausted air.
 3. The diverter/diffuser system of claim 1, wherein the diffuser includes a sound deadening material in the diffuser.
 4. The diverter/diffuser system of claim 1, wherein the diffuser includes: a. A lower intake chamber for receiving air and abrasive flow from the diverter; b. An upper expansion chamber; c. A restrictor plate between the lower intake chamber and the upper expansion chamber; d. The upper expansion chamber further including an exhaust port for releasing air and abrasive from the system.
 5. The diverter/diffuser system of claim 2, further including a baffle plate between the expansion chamber and the exhaust port.
 6. The diverter/diffuser system of claim 2, wherein the flow restrictor is a baffle plate in the path of the air and abrasive flowing through the diverter.
 7. A diffuser for use in connection with a blast system for diffusing exhausted air and abrasive during shutdown, the diffuser comprising: a. A lower intake chamber for receiving air and abrasive flow from the diverter; b. An upper expansion chamber; c. A restrictor plate between the lower intake chamber and the upper expansion chamber; d. The upper expansion chamber further including an exhaust port for releasing air and abrasive from the system.
 8. The diffuser of claim 6, further including a sound deadening material in the expansion chamber.
 9. The diffuser of claim 8, wherein the sound deadening material is a sheet material covering the walls of the expansion chamber.
 10. The diffuser of claim 6, including a baffle system in the expansion chamber between the restrictor plate and the exhaust port.
 11. The diffuser of claim 6, wherein the diffuser includes a deflection element for redirecting the air and abrasive received from the diverter and any residual abrasive media flowing through the back through the diverter.
 12. The diffuser of claim 11, wherein the deflection element is removable and replaceable.
 13. The diffuser of claim 12, wherein the diffuser includes a flow restrictor for reducing the noise level of the exhausted air, and wherein the deflection element is upstream of the flow restrictor. 